JUnit is an open source framework designed by Kent Beck, Erich Gamma for the purpose of writing and running test cases for java programs. In the case of web applications JUnit is used to test the application with out server. This framework builds a relationship between development and testing process.

Problems that we are facing in testing the applications

If we want to test any application, In standalone, we need to call the respective method’s main() method but there are so many problems in testing the flow using main() method.

In a web application, to test the flow we need to deploy it in the server so if there is a change then again we need to restart the server. Here also facing problems while testing the application.

Writing main method checks is convenient because all Java IDEs provide the ability to compile and run the class in the current buffer, and certainly have their place forexercising an object’s capability. There are, however, some issues with this approach that make it ineffective as a comprehensive test framework:

There is no explicit concept of a test passing or failing. Typically, the program outputs messages simply with System.out.println; the user has to look at this and decide if it is correct.

main has access to protected and private members and methods. While you may want to test the inner workings of a class may be desired, many tests are really about testing an object’s interface to the outside world.

There is no mechanism to collect results in a structured fashion.

There is no replicability. After each test run, a person has to examine and interpret the results. The JUnit framework addresses these issues, and more

Advantages of JUnit

JUnit addresses the above issues, It’s used to test an existing class. Suppose, If we have Calculation class then, we need to write CalculationTest to test the Calculation class.

Using JUnit we can save testing time.

In real time, in the web application development we implement JUnit test cases in the DAO classes. DAO classes can be tested with out server.

With JUnit we can also test Struts / Spring applications but most of the time we test only DAO classes. Even some times service classes also tested using JUnit.

Using JUnit, If we want to test the application (for web applications) then server is not required so the testing becomes fast.

Here if we run application, it will show whether the test cases have passed or not. If all test cases are passed then, it will show green indicator in the IDE. It will show red color to indicate that some or all of the test cases have failed.

Coding conventions while writing JUnit Test Cases

+—>Name of the test class must end with "Test".
+—>Name of the method must begin with "test".